Japanese patent application published on 29 Sep. 2005 under the No JP 2005-264086 describes blends of polystyrene (PS) and PLA in which PLA is the major part.
Japanese patent application published on 18 Jan. 2000 under the No JP 2000-017038 describes an expandable resin having biodegradability. This composition is made essentially of PLA and comprises 25% or less by weight of PS.
U.S. Pat. No. 7,160,948 in example 1 describes a composition as follows: 26.3% by weight of polylactic acid, 26.3% by weight of polymethyl methacrylate, 11.6% by weight of polyolefin and 35.8% by weight of a block copolymer of methyl methacrylate and styrene, said block copolymer comprising 30% of PS. This means clearly that the polystyrene is not the major part of the composition.
Japanese patent application published on 8 Dec. 2005 under the No JP 2005-336666 describes lactic acid fibers containing by weight 3 to 15% of syndiotactic polystyrene.
WO 92-04413 describes blends of PLA and general purpose polystyrene comprising by weight 10 to 25% of PLA. These blends are made by compounding PLA and PS.
WO 2007015448 describes a resin composition reduced in environmental burden which is excellent in strength, impact resistance, heat resistance, and moldability and which can be produced while attaining a reduction in CO2 discharge amount. The resin composition comprises (A) a styrene resin, (B) an aliphatic polyester, and at least one member selected between (C) a compatibilizing agent and (D) a dicarboxylic anhydride. The compatibilizing agent (C) preferably comprises one or more of the following. (C-1) A polymethyl methacrylate polymer (C-2) A vinyl polymer obtained by copolymerization with an epoxy or an acid anhydride (C-3) A graft polymer obtained by graft-polymerizing methyl methacrylate with a rubbery polymer (C-4) A block copolymer comprising a polylactic acid segment and a vinyl polymer segment bonded thereto. Said composition is made by compounding.
WO2006097979 describes a vegetable resin composition comprising polylactic acid, a thermoplastic resin, and a compatibilizing agent, wherein the compatibilizing agent is a polymeric material formed from a monomer ingredient comprising at least one alkyl methacrylate and has a weight-average molecular weight of 950,000 to 4,100,000. The alkyl methacrylate preferably is at least one member selected among methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. When this vegetable resin composition is used to form a molded vegetable resin, this molded vegetable resin can have improved impact resistance and improved heat resistance. Said composition is made by compounding.
JP200632831 A published on Dec. 7, 2006 provides a foamed sheet of a thermoplastic resin, having excellent extrusion characteristics at production of the foamed sheet, also having excellent rigidity, modulus, heat insulation, cold resistance, cushioning characteristics and the like, and capable of being secondarily processed to various kinds of containers or the like; and to provide a method for producing the container having excellent heat resistance. The foamed sheet is obtained by using a resin composition as a raw material, obtained by compounding (D) a compatibilizer of 1-20 pts.wt. with the total of 100 pts.wt. of three components consisting of (A) a polylactic acid of 20-90 wt. %, (B) a polystyrene-based resin of 5-65 wt. % and (C) a polypropylene-based resin of 5-40 wt. %, and has 1.1-5.0 expansion ratio and 0.5-3.0 mm thickness.
It has now been discovered a very simple process to make a composition comprising a monovinylaromatic polymer and one or more dispersed phase(s) made of one or more bio-sourced polymer(s) such as poly(hydroxy carboxylic acids) and/or cyclic carbonates, possibly incorporating an epoxide and carbon dioxide. The monovinylaromatic monomer is preferably styrene and the bio-sourced polymer is preferably lactic acid or lactide, its cyclic dimer (3,6-dimethyl-1,4-dioxane-2,5-dione).